P
[email protected]
- Jan 1, 1970
- 0
In another thread the point was raised that at least for high voltage or
high current levels, solid state switching can only be done at AC zero
crossing points. I am doubtful of some of the information posted, but
more so because the information seems incomplete or inconsistent, rather
than technical correctness.
Switching at other than zero crossing certainly must be taking place in
various devices. Lighting dimmers are one example where the AC cycle is
itself chopped at various points other than the zero-crossing. Merely
acting on incoming DC is a general example, since DC has no zero-crossing.
The discussion that raised the point involved high voltage DC or back to
back AC frequency conversion at high voltage. Voltages in excess of 100kV
would be involved. High currents would involved as well. The examples of
contradiction are low voltage (under 600 volts) cases. However, there is
the possibility of high currents even in the low voltage cases.
What I would like to know is, specifically for controlled switching (e.g.
not for ordinary rectifiers), what is the current state-of-the-art of
available products, and actually used products, in terms of what is the
maximum levels of voltage and/or current that can be switched. This might
need to be answered separately for a single solid state component and for
a stacked arrangement of components to increase voltage and.or current.
Do DC-to-AC inverters actually use pulse width modulation or pulse density
modulation technology to produce sine wave approximations from a single
DC voltage? Or is the state of the are in inverter technology still based
on "analog amplifier" or other technologies?
I've reviewed a wide range of inverters of interest and beyond interest.
One thing I have found in the technical descriptions of these devices is
that no one reveals the type of technology used to achieve the claimed
performance in terms of sine wave quality. They don't even say if they
are using pulse width modulation or pulse density modulation. Maybe they
are not using any of these methods at all.
I would like to know what frequencies are being used to generate the
sine waves in these devices to evaluate particular issues, such as RFI
or even health hazards.
For the simplest and/or most efficient design, what is the optimal ratio
of voltage between incoming DC voltage and direct (before any transformer)
outgoing AC (RMS) voltage?
Is it feasible to do pulse width/density modulation on 480 volts DC to
produce a waveform than can be filtered easily (with a minimum of LC
components) to 240 volts AC at 50 Hz or 60 Hz (before any voltage
changing transformer stage)?
high current levels, solid state switching can only be done at AC zero
crossing points. I am doubtful of some of the information posted, but
more so because the information seems incomplete or inconsistent, rather
than technical correctness.
Switching at other than zero crossing certainly must be taking place in
various devices. Lighting dimmers are one example where the AC cycle is
itself chopped at various points other than the zero-crossing. Merely
acting on incoming DC is a general example, since DC has no zero-crossing.
The discussion that raised the point involved high voltage DC or back to
back AC frequency conversion at high voltage. Voltages in excess of 100kV
would be involved. High currents would involved as well. The examples of
contradiction are low voltage (under 600 volts) cases. However, there is
the possibility of high currents even in the low voltage cases.
What I would like to know is, specifically for controlled switching (e.g.
not for ordinary rectifiers), what is the current state-of-the-art of
available products, and actually used products, in terms of what is the
maximum levels of voltage and/or current that can be switched. This might
need to be answered separately for a single solid state component and for
a stacked arrangement of components to increase voltage and.or current.
Do DC-to-AC inverters actually use pulse width modulation or pulse density
modulation technology to produce sine wave approximations from a single
DC voltage? Or is the state of the are in inverter technology still based
on "analog amplifier" or other technologies?
I've reviewed a wide range of inverters of interest and beyond interest.
One thing I have found in the technical descriptions of these devices is
that no one reveals the type of technology used to achieve the claimed
performance in terms of sine wave quality. They don't even say if they
are using pulse width modulation or pulse density modulation. Maybe they
are not using any of these methods at all.
I would like to know what frequencies are being used to generate the
sine waves in these devices to evaluate particular issues, such as RFI
or even health hazards.
For the simplest and/or most efficient design, what is the optimal ratio
of voltage between incoming DC voltage and direct (before any transformer)
outgoing AC (RMS) voltage?
Is it feasible to do pulse width/density modulation on 480 volts DC to
produce a waveform than can be filtered easily (with a minimum of LC
components) to 240 volts AC at 50 Hz or 60 Hz (before any voltage
changing transformer stage)?
